The tissue culture of human carcinomas is of potential value to biochemical, immunological, and pharmacological characterizations of malignant cells. The growth of colonic cancer presents unusually difficult problems with respect to the control of infection, and there is a tendency for fibroblasts to dominate the cultures. While there are limited numbers of established lines of cells, there is no reported method which permits the culture of malignant cells from most colonic carcinomas. The value of any cell line as a model for studies of colonic carcinoma is dependent upon the retention of the properties of the cells obtained from the surgical specimen. Methodology for the purification of malignant cells will permit the first study of the culture of colonic carcinoma in which primary cultures will be inoculated with purified, malignant, epithelial cells. Inoculation with purified cells will result in the reduction of the possibility of the overgrowth of cultures by fibroblasts or microorganisms and will permit the characteriation of specific cells from primary cultures as well as from later generations. The inoculation of primary cultures with purified cells will permit the evaluation of methods of tissue culture as they relate to the epithelial cells from a large number of colonic carcinomas. We shall attempt to obtain long-term cultures from a large number of carcinomas.